I personally for 95% of the time have it in AI SERVO and Single point focus and spot focus if focusing on a birds eye etc.
That suits me for chasing kids, birds and action.
Occasionally I use it in the Zone AF but then only the middle bit with 9 points, I don`t have the full 19 zone active its ( I switched it off in the menu ) too easy for the camera to focus on something in the foreground.
For the other 5% its in one shot AF.

For group photos the 9 zone af should be ok and aperture of 5.6-8 depending on how far you are away, do you use a flash then?

If you are closer aperture needs to be stepped down, otherwise some will not be in focus. But try single point focus on someone in the middle and see how its goes with aperture stepped down to 7-9.

I also have the focus point display on, so it shows a red square wherever you had the focus point, useful to work out where you have gone right or wrong.

I almost always leave it in evaluative metering, it works really well. Spot metering can be handy with some birdshots, but can be hit or miss, as it has a very small margin of error and doesn`t do bright or dark birds very well. ie If a white seagull or Cockatoo is fairly close it underexposes.
I just increase or decrease exposure by tad when required in evaluative metering, I have the highlight warning turned on to see when things are blown out.

Depending on the situation, you could keep everyone in a line and (making sure they are in a straight line) you could theoretically use a smaller f-number and get maximum blur in the background. If you're stacking people 4 rows deep, get a bigger f-number (5.6-8) and focus on the 2nd row of faces. Your DoF should buy you enough sharpness across the depth of the group, but it ultimately depends on how close they are and which lens you're using. There isn't really a one-size-fits-all solution.

As for focus modes, in addition to what maxjj said, set the Custom Function IV-1 and change the Depth of Field Preview button to switch between AI Servo and One-Shot AF modes. I usually roll with AI Servo but when I'm doing posed portraits instead of chasing the action I can focus more accurately with the One Shot mode simply by holding the button down. I can then go immediately back to chasing action again without even thinking about it.

I'd suggest avoiding the Zone or All-area AF modes if you're shooting a group because there are going to be a lot of interesting things your AF will want to grab focus on, and those things may not necessarily be what you want. Stick with Single point, manually-selected AF and that way you're in total control (which seems to match what you want with your exposure modes).

Thanks Plymer & maxjj for your advice,I will give all that a go when i get out with my camera,I do have a flash maxjj,I have the 580EX II,But thats another story as ive not got to grips with that,do you know much about this flash,thanks again